Self-contained perforating and countersinking unit



-w t t. 4- s March 15, 1960 F. M. BELDING 2,928,450

SELF-CONTAINED PERFORATING AND COUNTERSINKING UNIT Filed Feb. 7, 1955VENTOR.

Franu's M fi m-n BY M afi orng /J i United States Patent SELF-CONTAINEDPERFORATING AND COUNTERSINKING UNIT Francis M. Belding, Kenmore, N.Y.,assignor to Wales- Strippit Corporation, North Tonawanda, N.Y., acorporation of New York Application February 7, 1955, Serial No. 486,425

' 1 Claim. (Cl. 153-21 The present invention relates generally toself-contained perforating units, and more particularly to aselfcontained perforating unit adapted to punch and countersink a holesimultaneously.

Devices of the type disclosed herein have been needed for some time bythe sheet metal industry where it is often desirable to punch a hole andcountersink simultaneously; for with a self-contained perforating unitthat will punch and countersink a hole simultaneously need for compositeor progressive dies will be avoided. With these dies the holes mustfirst be punched and then these holes must be accurately registered withthe countersinking unit in order to countersink the holes. Heretofore,however, where attempts have been made to use a self-contained unit forsimultaneously punching and countersinking a sheet metal piece, thepunch has had to be solid enough to perforate the workpiece, which hasmeant a substantial column. This, in turn, has meant that when thecountersinking portion of the punch is bottomed, the punch itself seatsagainst solid metal; and the pressure of the press ram on the punch istransmitted directly through the punch to the die of the unit and to thebed of the press. As a result, extremely high stress levels are producedin the punch, with consequent failure of the mechanism, and inparticular of the punch. Generally, the life of conventionalself-contained perforating units for punching and countersinking a holesimultaneously, has been extremely short.

In some instances, stop-blocks have been used on the press to preventoverloading the punch members. When stop-blocks are used, however, thehigh forces developed are usually transmitted to the press itselfbecause a press by nature is a piece of heavy equipment and cannot beaccurately set to stop on its downward stroke within precise limits.

' Despite their short life and other disadvantages the use ofconventional perforating units for punching and countersinking has beenjustifie d because of thereduction in overall cost as compared with thecost of the complex dies required where punching and countersinking areused for perforating in a countersinking application, for,

in many instances it is possible to do the countersinking withoutfailure of the unit, because the spring-stripper provides the unit withthe required compensating resiliency. Since it is difficult, however, tohold a tool, which has to both perforate and countersink, very accuratein length, that is, to an accuracy of less than .001, and

since it is also extremely difficult to adjust the shut height of thepress close enough so that simultaneous perforatice ing andcountersinking can be done without a high rate of failure of thepunches, the problem is presented of achieving resiliency in such waythat suflicient force can be transmitted to the punch member to enableit to per:

forate and countersink a workpiece, while preventinga buildup in stresslevels to a point where, because of overtravel-of the press ram,inaccuracy in the length of the punch, or the like, the punch will befractured. In the past all attempts to use, for this purpose, rubber orother resilient devices have failed. This is because such high forcesmust be transmitted through the resilient medium, that the resilientmember had to be so large that it has rendered the unit itselfimpractical. Moreover, none of the resilient mediums heretoforeavailable were suitable for the purpose. As a result, in most instancesit has been preferred to overload the punch or the stop blocks, and toreplace these parts when they failed.

When stop blocks are used, however, extreme accuracy in manufacture ofthe punching units is still required to control the distance from thehead to the countersink very accurately, as well as the height of thedie member, and of the holder to which the unit is attached. Tolerancesin the neighborhood of .0002" are necessary on these parts of the unitto prevent excessive buildup'in stress levels with resultant earlyfailure of the units. Even when such close tolerances are maintained,poor countersinking by some of the units, where a multiple unit set-upis used, sometimes occurs because of this .0002" tolerance.

An alternative, when a number of perforating and countersinking unitsare to be used for simultaneous operation on a workpiece, is to take theunits after they have all been assembled and to grind the punches to thesame identical lengths, when closed. This is time-consuming and costly,and prevents the interchangeability of punches and other parts, normallyassociated with a mass pro-' duction operation.

One object of this invention is to provide a nonbottomingperforating-oountersinking unit.

Another object of this invention is to provide in a countersink type ofperforating unit means for compensating for a buildup in tolerances inthe several parts of the unit.

Another object of this invention is to provide perforat-'ing-countersinking apparatus in which commercial parts may be used toprovide a non-bottoming perforating unit.

Another object of the invention is to provide a counter sink type ofperforating unit, which will eliminate failure of punches when aplurality of them are used simultaneously for multiplepunching-countersinkirig operations on a workpiece.

Another object of this invention is to provide perforating-countersinking apparatus of the character described which hasincorporated therein resilient means for preventing excessive buildup instress levels.

Another object of this invention is to provideperforating-countersinking apparatus which will have a vastly longerlife than similar units of prior design, but which at the same time willbe reasonable in cost.

Other objects of this invention will be apparent hereinafter from thespecification and from the recital of the appended claims.

In the drawing:

Fig. l is a side elevation of a perforating. unit constructed accordingto one embodiment of this invention, the unit being shown with the toolin withdrawn, nonworking position;

Fig. 2 is a fragmentary section taken on line 2-2 of Fig. 1 looking inthe direction of the arrows, illustrating on an, enlarged scalethe'structure of the punching, countersinking assembly and showing aworkpiece'disposed on the die in position to be punched and countersunk,the punch and the parts associated therewith being shown in withdrawn,non-working position; and

Fig 3. is a section similar,tQ FigMZ, .buttshowin'g the.

positions of the: parts Ton completion of a Working stroke ofthe punch.Q I j e W Q Referring-nowto the drawing by numerals of reference,

20 denotes generally a self-contained perforating-counter:

sinking unit constructed according to one embodiment of this invention.The unit comprises, generally; a Q-frame Die member 22 has a centralbore 32; formed withv a conical portion 33 at its'upp'er end, andcommunicating with a discharge chute 34 through which slugs punched froma workpiece W may be discharged. i

The punch-countersink-stripper assembly 23 comprises escapee toaccurately adjust the stroke of the ram of a heavy I punch press,capable of producing say a two hundred toir force, within a fewthousandths of an inch. That is why,

as stated above, it has been necessary in the past to put heavy stopblocks in the'press to prevent the ram from overloading the. perforatingunits. However, as also stated, this'simply transfers the stress fromthe punch member-to the. bed and rain of the press, often causingfailure of the press.

The diificulties and disadvantages of previous apparatus may be avoidedin the perforatorcountersinker of the present inventionbyprovidingpunch-stripper assembly 23.

t with. a cap member 65 which is adapted to be engaged by ram R (Figs.2' and 3) of the press; Cap 65 ismade of a resilient materiaLpreferablynylon. It is formed with a skirt portion 66, which nests over the punchhead 41 and the upper end of stripper-spring 55. v Skirt 66 has aninside diameter equal to or even slightly less than the i outsidediameter of head 41 and ofspring 55. Thus,

the tool 40, the tubular, combined stripper and guide mem- 1 her 50, acoil spring 55; and a secondary lifter. spring 60.

,Member 5ii-is reciprocable in bore 37 of theupper arm of holder 21.Coil spring 55 surrounds the tool 40 and theupper, neck portion 52 ofstripper 50, and is interposed between the head. 41 of the tool and theupper f-ace51 of a collar 53* formed on the stripper 50. Lifter spring60 surrounds xthelstripper sleeve 50 and is interposed betweentthelower. face 54 of this collar and the upper surface of arm 25. 'Lifterspring 60 acts to hold the assembly- 23 in raised position. (Figs. 1 and2.) to provide clearance for the insertion of workpiece W between thetooland die.

Referring now to Fig. 3 it will be noted thatthe tool or punch member40, instead of having just a punch tip 42 on it, has also a conicalcountersink portion 43 formed thereon. above; punch tip 42. Countersinkportion 43 is complementary to the mating countersink portion 33 formedin the die member 22. Countersink portion 43 connects the tip 42 of thetool with the shank 44- ofthe tool. The shank 44 is mounted toreciprocate in and to be guided, by the bore of stripper sleeve 50;Above the stripper sleeve the tool shank is of increased diameter whenit is pressed onto the head 41 and spring 55 it will grip theperipheries of these parts and stay in place. .As a result, whentheimplement is transported there is no danger of cap 65 falling off.

.On punching andcountersinking operations, the elastic member 65'servesto transmit the force of the ram R to the punch head 41; and. at thesame time it provides resiliency. between the ram and the punch. If thestroke of the ramis in excess of that proper for the length of the.

punch," or if. a punch inla multiple perforating tool set-up as denotedat 45. Portion 45 of the 'tool'shank connects V with. thetool head 41.

In operation, the ,tool 40 descends and its part 42 punches a slug; outof the workpiece into the die; after whichcontinued downward movement ofthe tool causes the tapered countersink portion 43 of the tool, incooperation with..the conical recess 33 in the die, to' form acountersink Cain workpiece W. This latter is the operation that hascaused the difficulties heretofore in achieving a practical tool forsimultaneously punching and countersinking a workpiece.

It willibe obvious that, if

the ram 'R of a'press. engages directly with the head 41 of the punch,the height of thearm 26, the height of the die 22 above its seat on arm26, the height or, length of the tool" 40, and the height of thestripper 50 must be held to absolute accuracy to avoid a buildup intolerance from one part to the other under the ram. Obviously this is aphysical impossibility and variations in total height as' high as .005"occur even with the most accuratemanu facture.

Wherethere are a plurality of holes to be punched and countersunksimultaneously in a workpiece by a plurality of perforating units, itmay become necessary even to grind the headsof the punches so that theyare all engaged simultaneously by the ram, but this renders the punchesno longer interchangeable. Even grinding of the heads of the punches maybe of no avail ifthe ram of the press has a taper or belly in iton itslower-face. Moreover, as previously} stated, itis extremely 'difiiculthappens: to bemore: than the. desired.1ength,.the cap:

is reduced in thickness and its skirt portion 66 is ex panded so thatitno longer hugs tool head 41 and;

'spring 55, The plastic cap 65 will therefore transmit the. pressure"required to press the countersink 43 of the 1 tool into the work piecewhileat the same time providing sufficient elasticity to insure that asafe limit stress i on the machine tool elements will not be exceeded.In

other words, the plastic cap 65 is, in effect, a safety valve preventingoverload of the tool 40, or of the press from the' perforating forces.

When the ram R is retractedupon completion of its working stroke, thestripper spring 55 expands in the usual fashion to strip the tool fromthe work; and then the lifter spring 60 lifts the wholetool-stripperassembly 23 back to the position shown in Figs. .1 and2.

cap 65 returns to its normal shape, skirt 66 againgiipping headf41 andspring 55.

The apparatus described W111 perforate. and cotmtersink a workpiece,simultaneously, with a degree of accuracy and efficiency heretoforeunattainable. The resilient member 65 in the implement transmits theworking force and at the same time positively prevents excessive buildup in stress'levels in the punch-countersink member. This'means that:the implement will have a long life. The use of stop-blocks on the pressis no,

longer retiuired. Also, any necessity for grinding in dividual punchesin an assembly operation is likewise eliminated, thus permittinginterchangeability of parts.

Further, the cost of manufacturing the implements greatly reducedbecause extremely close tolerances need not be maintained. Nylon member65 need not be pre cision' made. A commercial part constructed with ap;proximatelythe desired length and diameter is-suflicient, as is apparentfrom the foregoing description.

While the invention has been described in connection with a'specificembodiment thereof, it will be understood that it is capable ofmodification, and this application is i'ntenderl'to cover anyvariations, uses or adaptationshf the invention following, in general,the principles of the invention and including such departures from thepresent disclosure as come withinknown or customary practice in? the artto which the invention pertains and as maybe applied to the essentialfeatures hereinbefore set forth and as fall within the scope of theinvention or the limits of the appended claim.

Having thus described my invention what I claim is:

A self-contained implement for use in a press for simultaneouslypunching and countersinking a workpiece, comprising a C-frame havingupper and lower arms, a die mounted on said lower arm, a stripper sleevereciprocably mounted in a bore in said upper arm in axial alignment withsaid die, a tool reciprocable in said sleeve, said tool having a shankportion of one diameter slidably guided in said sleeve, a punch bit ofreduced diameter at its lower end, a conical countersink portionconnecting said punch bit with said shank portion, and an enlarged headat its upper end, said die having a bore, to receive said punch bit,which has a conical portion at its upper end to cooperate with theconical countersink portion of said tool, a coil stripper-springinterposed between said stripper sleeve and said head, and acompressible, distortable, resilient plastic cap mounted on top of saidhead, said cap having a depending skirt which surrounds the periphery ofsaid head and the upper end ,of said spring, and which resilientlyembraces said spring in the normal position of said cap but which isfree thereof, said cap being adapted to transmit the working force ofthe press to said tool, said cap being distortable and deflectable toprotect the tool from being over-stressed,

said skirt expanding away from said headand from said spring when saidcap is distorted. p 7

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